Conventional armor-piercing military projectiles employ one-piece materials such as hardened steel or encased sub-caliber core materials such as tungsten carbide or the like. Ideally, these conventional projectiles perform their function by acting as a high speed punch to penetrate the target armor. During penetration, the conventional projectile will normally experience cracking and consequent breakup. Against oblique targets the breakup or shattering is greatly accentuated. Consequently, the full penetration capability of the projectile is not realized because the material lacks sufficient resistance to brittle fracture under these conditions. The shock wave phenomenon which assists in the destruction of the target armor in the ideal condition may cause the failure of the projectile in the latter situation. The mechanics of this failure will be discussed later.
One remedy for this failure mode would be to increase the ductility of the projectile so as to provide more shock absorbency. However, the results will again be unsatisfactory, because plastic deformation of the projectile will both dissipate its kinetic energy and also result in a larger frontal area as "mushrooming" occurs, thereby decreasing the ability to penetrate.
Applicants propose a compound projectile to solve these problems. Applicants' projectile includes outer relatively hard laminations intended to readily pierce target armor plate, and an inner relatively tough and ductile core intended to maintain the projectile integrity during its passage through the armor plate. It is understood however, that the core could also be made of a plurality of laminations, and therefore, the complete projectile could be constructed of laminations.
Other inventors have developed compound projectiles of various designs to counter difficulties arising in other ballistic conditions. Walker U.S. Pat. No. 2,792,618 teaches a dual jacket bullet for hunting which features an inner jacket of mild steel or copper running axially from the trailing edge to the midpoint of the projectile. Walter suggests this construction as a mechanism to facilitate expansion or "mushrooming" of the bullet's unreinforced soft metal ogive while preventing complete disintegration of the projectile. Frost U.S. Pat. No. 2,751,845 discloses a two-piece bullet comprising a soft metal base having a mushroom shaped projection running axially forward from its trailing edge so as to lock the lead slug nose into place, thereby preventing separation of the two components upon impact. Crane and Fox U.S. Pat. No. 57,870 describe an artillery shell composed of non-bonded, concentrically cast, metallurgically identical lamellae, with each successive lamination cast upon the previous layer. Crane and Fox developed this construction because their research indicated that many more shell fragments result from the breakup of a non-bonded laminated projectile than are produced by a homogeneous mass having an identical explosive charge contained in a central cavity. Zaid et al. U.S. Pat. No. 3,680,485 disclose a series of like projectiles "nested" together for handling purposes, which separate axially while traveling down the gun barrel and leave the muzzle as a series of discrete projectiles.
The foregoing discussion discloses the significant differences between the applicants' projectile and the related prior art. Neither Walker nor Frost teach the use of continual, axially-running concentric laminations of high-strength materials. Therefore, these earlier designs are unsuitable for armor piercing because their monolithic ogives are subject to the brittle fracture and excessive expansion problems. Similarly, the Crane, Fox, and Zaid structures are not comparable to the applicants' projectile in either structure or function. None of the prior art inventors contemplated the use of their teachings to defeat ballistic armor, and this fact is evidenced in the unsuitability of their projectiles for this purpose.